1. Field of the Invention
This invention relates to an apparatus for developing photographic images on an emulsion layer coated on a photographic film base and more particularly to an apparatus utilizing heating elements with forced air flow to establish a gas bearing to support the film and conductively heat the film at high temperatures for rapid image development.
2. Description of the Prior Art
In photographic systems it is often desirable to visually display photographic images in a short time subsequent to the forming of the images on a sensitized photographic surface. Such photographic systems are useful, for example, in reconaissance and weather applications, aircraft and space use and commercial systems requiring fast display response. In these systems, dry development of photographic images on the sensitized film by thermal processing subsequent to exposure of the sensitized surface to light generally can be more time consuming than the exposure process.
In a conventional device for developing photographic images, a light-sensitive, heat-developable emulsion layer such as a dry silver halide is coated on a suitable film base or support. The dry silver emulsion contains photosensitive silver halide, an organic silver salt, and a reducing agent. Exposure to a light-image generates from the silver halide component a catalyst which accelerates the image-forming reaction between the other two components to make possible the subsequent heat development of the visable image. The typical dry silver film development temperature range of these conventional thermal processing devices is about 210.degree.-330.degree. F. (99.degree.-166.degree. C.), and generally the development time is for 30 seconds at 260.degree. F. (127.degree. C.).
Since the photographic film development is a chemical reaction, the development time can be shortened by raising the processing temperature. However, thermal warping and weakening of the base can occur at temperatures in excess of 330.degree. F. (166.degree. C.). Furthermore, contacting the emulsion at a temperature in excess of 330.degree. F. (166.degree. C.) is not desirable since the emulsion is relatively soft and more easily damaged. Thus, standard film development devices utilizing "hot" rollers for thermal processing which contact the emulsion of the film are inadequate for reducing the film development time by use of higher processing temperatures. Moreover, development devices employing thermal radiation or convective heat transfer mediums often lack the control of localized heating and accurate maintenance of temperature levels to satisfactorily provide uniform film development or to effectively reduce the time of film development.